Helicity characteristics of sunspot umbra and penumbra

Hao Juan, haojuan@nao.cas.cn, National Astronomical Observatories, Chinese Academy of Sciences, China
Zhang Mei, zhangmei@nao.cas.cn, National Astronomical Observatories, Chinese Academy of Sciences

Abstract
Non-potentiality of solar magnetic field is mainly expressed by helicity. Studying helicity of active regions has important scientific significances to the understanding of dynamo theory, origins of solar cycle and solar activities. Observations have shown that statistically there exists a hemispheric helicity sign rule, that is, positive helicity sign in the southern hemisphere and negative helicity sign in the northern hemisphere. However, a recent large-sample statistical result has shown that strong and weak magnetic fields show opposite helicity signs. A very recent research also gives example of sunspots where umbra with strong magnetic field shows opposite helicity sign to that of penumbra. In this talk, we will use SP/Hionde data, as the so-far most accurate magnetic field measurement, to statistically study the helicity characteristics in sunspot umbra and penumbra, how they may affect the estimation of the helicity sign of the entire active region and even affect the accurate measurement of hemispheric helicity sign rule.